Effects
The simplicity of electrical synapses results in synapses that are fast, but can only produce simple behaviors compared to the more complex chemical synapses.
- Without the need for receptors to recognize chemical messengers, signal transmission at electrical synapses is more rapid than that which occurs across chemical synapses, the predominant kind of junctions between neurons. The synaptic delay for a chemical synapse is typically about 2 ms, while the synaptic delay for an electrical synapse may be about 0.2 ms. However, the difference in speed between chemical and electrical synapses is not as marked in mammals as it is in cold-blooded animals.
- Because electrical synapses do not involve neurotransmitters, electrical neurotransmission is less modifiable than chemical neurotransmission
- The response is always the same sign as the source. For example, depolarization of the pre-synaptic membrane will always induce a depolarization in the post-synaptic membrane, and vice versa for hyperpolarization.
- The response in the postsynaptic neuron is generally smaller in amplitude than the source. The amount of attenuation of the signal is due to the membrane resistance of the presynaptic and postsynaptic neurons.
- Long-term changes can be seen in electrical synapses. For example, changes in electrical synapses in the retina are seen during light and dark adaptations of the retina.
The relative speed of electrical synapses also allows for many neurons to fire synchronously. Because of the speed of transmission, electrical synapses are found in escape mechanisms and other processes that require quick responses, such as the response to danger of the sea hare Aplysia, which quickly releases large quantities of ink to obscure enemies' vision.
Normally, current carried by ions could travel in either direction through this type of synapse. However, sometimes the junctions are rectifying synapses, containing voltage-gated ion channels that open in response to depolarization of an axon's plasma membrane, and prevent current from traveling in one of the two directions. Some channels may also close in response to increased calcium (Ca2+) or hydrogen (H+) ion concentration, so as not to spread damage from one cell to another.
There is also evidence for "plasticity" at some of these synapses—that is, that the electrical connection they establish can strengthen or weaken as a result of activity.
Electrical synapses are abundant in the retina and cerebral cortex of vertebrates.
Read more about this topic: Electrical Synapse
Famous quotes containing the word effects:
“The best road to correct reasoning is by physical science; the way to trace effects to causes is through physical science; the only corrective, therefore, of superstition is physical science.”
—Frances Wright (1795–1852)
“Upon the whole, necessity is something, that exists in the mind, not in objects; nor is it possible for us ever to form the most distant idea of it, consider’d as a quality in bodies. Either we have no idea of necessity, or necessity is nothing but that determination of thought to pass from cause to effects and effects to causes, according to their experienc’d union.”
—David Hume (1711–1776)
“Like the effects of industrial pollution ... the AIDS crisis is evidence of a world in which nothing important is regional, local, limited; in which everything that can circulate does, and every problem is, or is destined to become, worldwide.”
—Susan Sontag (b. 1933)